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914World.com _ 914World Garage _ proportioning valve
Posted by: trekkor May 9 2005, 05:53 PM
I'll be covered in Motul before too long. 
Was kicking around the idea of opening up the prop valve and taking it all apart, rendering it a "tee".
Anybody done this?
Sure, just using a "tee" is easier. This is just something to do.
Exploded view would be nice.
KT
Posted by: Jeroen May 9 2005, 06:05 PM
buy a friggin' T 
Posted by: Mueller May 9 2005, 06:05 PM
it's been a while since I've seen the insides of one, but I think you might have difficulties getting the air removed.
Posted by: jkeyzer May 9 2005, 06:05 PM
Do a search here and also on PP. I have seen a diagram before. I think it was on PP. Someone had one completely apart showing all the components.
PS. A tee is significantly lighter. 
Posted by: Travis Neff May 9 2005, 06:16 PM
I would also think that it would be a bleeding nightmare the first go-round. aside from that, having a resivour (that is what it would essentially be) partway through the brake system - is that an OK thing to have?
Posted by: Series9 May 9 2005, 06:52 PM
Save yourself a bunch of trouble by going down to your local air-cooled VW specialist and buying a T for $5.
Posted by: McMark May 9 2005, 06:57 PM
To clarify Trekkor's first post. He knows the T is "better" and has one on order. But let's think about what we could do. Is gutting the P-Valve a viable alternative?
It's not should he, but could he.
Posted by: bondo May 9 2005, 06:58 PM
Haha, if you want something to do... I have a transmission that needs assembling! 
Posted by: Mueller May 9 2005, 07:14 PM
exploded pic:
I see the two lines which I think go to the rear calipers....
now I cannot remember where the other line goes to.....
should be 3 total correct??
Posted by: lapuwali May 9 2005, 07:17 PM
| QUOTE (Mueller @ May 9 2005, 05:14 PM) |
| exploded pic: I see the two lines which I think go to the rear calipers.... now I cannot remember where the other line goes to..... should be 3 total correct?? |
The fluid as to come in somehow...
Posted by: Cloudbuster May 9 2005, 07:19 PM
I suppose any spaces in the proportioning valve body that can become air traps could be filled in with some chopsticks...
Posted by: Aaron Cox May 9 2005, 07:21 PM
| QUOTE (Cloudbuster @ May 9 2005, 06:19 PM) |
| I suppose any spaces in the proportioning valve body that can become air traps could be filled in with some chopsticks... |
and mike....its the inlet from the MC
Posted by: lapuwali May 9 2005, 07:30 PM
The fluid normally comes in from the MC, and flows through those holes in the silver piston. Another passage in the housing also applies brake pressure to the silver piston to the right (in this pic) of the rightmost O-ring on that piston. This forces the piston to the left against that big spring, which closes off the holes in the piston. Eventually, the holes close completely and the rear brakes are cut off entirely.
You can also stiffen up the spring by placing some thick washers under that thin plate at the left end of the spring. This pre-loads the spring, so it takes more brake pressure to push the piston to the left, thus giving you more rear brakes. If you want to turn it into a big, heavy tee, then remove the spring and replace it with a bit of steel tube. You'll need to determine the correct length of tube, as I'm sure the spring is slightly compressed when everything is assembled, so you can't just use the free length of the spring.
I initially thought you could just remove the spring and the piston, but I think that will require you to add a lot of brake fluid to fill up that part of the housing that holds the spring. It looks like the piston normally seals that part off (see the leftmost O-ring), so only the area between the two O-rings has brake fluid in it, as well as the area to the right of the rightmost O-ring (note the O-ring on the end plug).
Posted by: boxstr May 9 2005, 07:41 PM
Received these today from JWEST. Thank you.
CCLINTEETIME
Attached image(s)
Posted by: brant May 9 2005, 07:48 PM
Trekor,
the only reason a person would do this would be due to stock type rules that do not allow you to run a "T" or run a proportioning valve...
surely that's not your motivation is it....
just teasing you
brant
Posted by: J P Stein May 9 2005, 08:00 PM
If you have stock F&R brakes, why the" T"? I imagine that Porsche (Vdub?) seemed to think they needed the porp. valve for a reason.....like maybe F to R balance?
If you feel the need to change sumthin', put in an adjustable proportioning valve to balance future upgrades.
Posted by: root May 9 2005, 08:53 PM
My "two-cents"; whatever modification you make always be sure to arrange the inlet side of a 'tee' on the bottom, unless you intend to reverse bleed the system, 'cause air bubbles like to go 'up' during bleeding. 
Posted by: 914GT May 9 2005, 10:12 PM
| QUOTE (Mueller @ May 9 2005, 06:14 PM) |
| exploded pic: I see the two lines which I think go to the rear calipers.... now I cannot remember where the other line goes to..... should be 3 total correct?? |
Inlet is at the bottom of the casting where it bumps out. You can essentiall get the thing to act as a T by turning the screw on the end all the way in, causing the internal coil spring to bind and prevent it from regulating the pressure to the rear brakes.
Posted by: McMark May 10 2005, 03:50 AM
Factory cutaway picture. There's a slight difference in the threaded hardline connections (same side vs. opposing sides), but the function should be the same.
Attached thumbnail(s)
Posted by: balljoint May 10 2005, 06:21 AM
Does brake fluid sit in the cylinder with the spring or is it sealed off from the system? If it is full of fluid then it is already essentially an extra reservoir in the middle of the system. If it is just air in there then will it leak fluid to the outside if the seal breaks down or will it leak air into the system? If it is leaking air into the brake lines without spilling brake fluid to the outside then it becomes a difficult to detect source of air in the line.
Posted by: 914GT May 10 2005, 08:26 AM
| QUOTE (balljoint @ May 10 2005, 05:21 AM) |
| Does brake fluid sit in the cylinder with the spring or is it sealed off from the system? If it is full of fluid then it is already essentially an extra reservoir in the middle of the system. If it is just air in there then will it leak fluid to the outside if the seal breaks down or will it leak air into the system? If it is leaking air into the brake lines without spilling brake fluid to the outside then it becomes a difficult to detect source of air in the line. |
There should be no fluid on the spring side. It might leak fluid if the piston seal went bad, but on two of them I've disassembled they were both good. I've heard of one-way leaks where air goes in but no fluid comes out but doesn't make much sense. The high system pressures will force fluid out if there are any bad seals or poor fittings, and air could be drawn back in once the brake pedal is released.
Posted by: Brad Roberts May 10 2005, 09:08 AM
| QUOTE |
| If you have stock F&R brakes, why the" T"? I imagine that Porsche (Vdub?) seemed to think they needed the porp. valve for a reason.....like maybe F to R balance? If you feel the need to change sumthin', put in an adjustable proportioning valve to balance future upgrades |
Ha ha.. F+R balance went out the window when we developed larger sticky tires and mucho better brake pads than what we had in 1970??
Oh.. Trekkor has a 6cyl now.. 6cyl 914's had larger rear pistons in the calipers with a different prop valve. Sooo.. stock 4cyl rear calipers...added weight... RUN THE TEE.
B
Posted by: trekkor May 10 2005, 09:15 AM
| QUOTE |
| RUN THE TEE |
I will. I'm just playing around.
KT
Posted by: tommy914 May 10 2005, 09:35 AM
I replaced the "stock" adjusting bolt on the end with one that was longer. This allowed me to pre-load the spring to a greater degree. It seems firmer.
Posted by: J P Stein May 10 2005, 12:46 PM
Sure , run the T. You can always change to an adjustable valve if your rears lock first.
I better get outta this before I insult someone.
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